A Korean study has found that coronary artery bypass grafting is associated with fewer risks than the less invasive method of angioplasty and insertion of stents.

Patients with multiple narrowed arteries in the heart receiving angioplasty with the new stents had a 47% higher risk of death, heart attack or subsequent procedure to clear blocked arteries, as compared to patients who received bypass.

Current medical guidelines recommend bypass surgery for treating patients with substantial narrowing in multiple arteries, a condition known as multi-vessel coronary artery disease.

Death, heart attack or a subsequent procedure to clear blocked arteries occurred in 15% of patients in the angioplasty group and 11% of patients in the bypass group.

Patients receiving angioplasty were twice as likely to need repeat revascularisation and more than 1.8 times as likely to have a heart attack as patients who received bypass.

The study was done on 880 patients treated at 27 hospitals in four countries. All patients had multi-vessel coronary artery disease and were equally appropriate candidates for either angioplasty or bypass.

Half of the patients were randomly assigned to receive angioplasty with the medicinal stent and half received bypass surgery. Patients were tracked for an average of more than 4.5 years.

The study, published online in the New England Journal of Medicine, is the second such randomised controlled trials to compare bypass to angioplasty since the introduction of everolimus-eluting stents that emit medication to prevent blood clots.

"Based on our data, CABG is still the preferred option for multivessel disease," said Seung-Jung Park, MD, a cardiologist at Asan Medical Center in Seoul, South Korea, and the study's lead author. "We had thought that previous trials may have been limited by their use of first-generation drug-eluting stents, but these results show CABG still leads to better outcomes."

However, the trial was discontinued due to slow enrolment after the introduction of a newer angioplasty technique called fractional flow reserve where surgeons are guided more precisely on the condition of arteries based on blood flow through them. A new study is under way to assess the method and compare it with coronary bypass.

CABG or heart bypass surgery is increasingly less favoured than angioplasty considered a less-invasive option where a stent is inserted to hold the arteries open. Advanced stents in the market have made it popular.

In bypass surgery, a vein or artery from elsewhere in the body is grafted onto a narrowed coronary artery to allow blood to flow to the heart more freely.